Single-cell protein facts for kids

Imagine tiny living things you can eat! That's what Single-cell proteins (or SCP) are. They're also called microbial proteins because they come from microorganisms. These tiny organisms, like algae, yeasts, fungi, or bacteria, can be grown in special ways. We can then use them as a healthy ingredient or even a replacement for foods rich in protein. They are good for both people and animals to eat!

Growing food the usual way, like farming, uses a lot of water and land. It can also harm nature and add to climate change by releasing gases. But making SCPs doesn't have these big problems. Today, SCPs are often grown using waste from farms. This means they still use some water and land from regular farming. However, SCPs can also be grown completely on their own, without farm waste.

Microbes are amazing because they can grow in many different ways. This means SCPs can help us recycle nutrients and are much more efficient than growing regular crops. For example, a study in 2021 showed that making microbial protein using solar power needed 10 times less land than growing soybeans for the same amount of protein.

The world population is expected to reach 9 billion people by 2050. Experts believe that traditional farming might not be able to feed everyone. This could lead to a serious risk of not having enough food. SCPs offer a reliable way to produce a lot of food, even when the weather is bad or climates are harsh.

The History of Single-Cell Proteins

Early Discoveries and War Efforts

People started finding ways to make concentrated forms of yeast way back in 1781. About a century ago, a scientist named Max Delbrück and his team found out that extra yeast from brewing beer was very good for feeding animals.

During World War I and World War II, Germany used yeast-SCP a lot. They needed it to help with food shortages during the wars. Some inventions for making SCP also helped biotechnology in general. For example, in 1919, scientists in Denmark and Germany found a new way to feed sugar water to yeast slowly. This was a big step forward!

Fighting Hunger After the Wars

After the wars, the Food and Agriculture Organization of the United Nations (FAO) focused on hunger. In 1960, they talked about the "protein gap." This meant that 25% of the world's people didn't get enough protein in their diet. There was also a worry that farming wouldn't be able to feed more and more people.

By the mid-1960s, a lot of food yeast was being made around the world. The Soviet Union alone made about 900,000 tons of food and animal feed yeast by 1970.

Oil and Protein: A New Idea

In the 1960s, scientists at British Petroleum came up with a new idea. They called it "proteins-from-oil process." This technology made single-cell protein using yeast that ate waxy n-paraffins. These paraffins were a leftover product from oil refineries.

The first research was done by Alfred Champagnat in France. A small test plant started working there in 1963. Another test plant was built in Britain. The term SCP was first used in 1966 by Carroll L. Wilson from MIT.

The idea of "food from oil" became very popular in the 1970s. Champagnat even won a science prize in 1976. Many countries built factories to make yeast fed by paraffin. This product was mostly used to feed chickens and cows.

The Soviet Union was very keen on this idea. They opened large "BVK" plants (which means "protein-vitamin concentrate") near their oil refineries. By 1989, they had eight such plants. However, people worried about harmful substances in the SCP from oil. Also, environmental groups pushed for change. So, the government decided to close these plants or change them to make other things.

Modern SCP Products

Today, you might know Quorn. It's a type of meat substitute made from a fungus called Fusarium venenatum. It's sold in Europe and North America. Other companies like Calysta, Unibio, Circe Biotechnologie, and String Bio also make SCP-based meat substitutes, some using bacteria instead of fungi.

How Single-Cell Proteins Are Made

Growing Microbes

Single-cell proteins are made when microbes grow using different materials. These materials can be waste products like wood, straw, or leftovers from food factories. They can also use hydrocarbons (like from oil) or even animal waste.

A newer way to make SCP is called 'electric food' processes. For this, the main things needed are electricity, CO₂ (carbon dioxide), and tiny amounts of minerals and chemicals.

Getting the Protein Out

One challenge is that the single-cell proteins are usually found in very small amounts in the waste materials. They are often less than 5% of the mix. Engineers have found ways to get more of them out. They use methods like spinning them very fast (centrifugation) or filtering them.

After being collected, the single-cell protein needs to be dried. It should have about 10% water left. Or, it can be made acidic. This helps it last longer and stops it from going bad. The machines needed for these steps can be expensive. It's often best to use the SCP product locally and soon after it's made.

Types of Microorganisms Used for SCP

Many different tiny living things can be used to make single-cell proteins. Here are some examples:

• Yeast
  • Saccharomyces cerevisiae
  • Pichia pastoris
  • Candida utilis
  • Torulopsis corallina
  • Geotrichum candidum
• Fungi (Mycoprotein)
  • Aspergillus oryzae
  • Fusarium venenatum
  • Sclerotium rolfsii
  • Polyporus
  • Trichoderma
  • Scytalidium acidophilum
• Bacteria
  • Rhodobacter capsulatus
  • Methylophilus methylotrophus
  • Metylococcus capsulatus
• Algae
  • Spirulina (dietary supplement)
  • Chlorella

Benefits and Challenges of Single-Cell Proteins

Amazing Advantages

Making large amounts of microbial protein has many good points compared to traditional ways of getting protein:

• Super Fast Growth: Microorganisms grow much faster than plants or animals. Algae can double in 2-6 hours, yeast in 1-3 hours, and bacteria in just 0.5-2 hours! This also means scientists can quickly find and grow the best types of microbes that give a lot of protein and are very nutritious.
• Use the Whole Thing: When we grow crops, we often only eat parts like fruits or grains. Stems, leaves, and roots are usually not eaten. But with single-cell microorganisms, we can use the whole tiny organism. Also, many microbes are much easier to digest than parts of plants.
• Packed with Protein: Microorganisms usually have a lot of protein. About 30-70% of their dry weight is protein. This is much higher than most vegetables or grains. The proteins in many SCPs are also very high quality, similar to the protein in eggs.
• Making Vitamins: Some microorganisms can make vitamins and nutrients that plants can't, or can't make much of. This includes important vitamins like B12.
• Eating Waste: Microorganisms can use many different things as food sources. These include alkanes, methanol, methane, ethanol, and sugars. Things that were once considered "waste" can be turned into food for these tiny organisms.
• Cleaning the Air: Like plants, some microorganisms can grow by using CO₂ from the air. Some bacteria are even better at capturing CO₂ than plants.
• Using Special Gases: Some bacteria can use a gas mixture called synthesis gas (syngas) as food. Syngas can be made from tough plant waste like wood.
• Making Their Own Fertilizer: Some bacteria can take nitrogen from the air. This means they don't need chemical nitrogen fertilizers. These fertilizers can harm the environment and our health.
• Powered by Electricity: Some bacteria can use hydrogen gas for energy. Hydrogen can be made using electricity and water. So, these bacteria can be "powered by electricity" to grow quickly without light.
• No Weather Worries: Growing microorganisms doesn't depend on seasons or weather. They can also be protected from extreme weather events. This is important as climate change is expected to cause more crop failures. Some microbes, like yeasts, can even grow at night.
• Less Water Needed: Growing microorganisms uses much less water than farming. Crops use a lot of water that evaporates or runs off. But SCPs grown in special containers don't have these water losses.
• No Need for Good Soil: Growing SCPs doesn't need fertile soil. So, it doesn't compete with farming for land. Because they need little water, SCPs can even be grown in dry places. This could help provide food in countries with dry climates.
• Better Use of Sunlight: Microorganisms that use sunlight can turn solar energy into food more efficiently than plants. This is because in special containers, we can control the water, CO₂, and light perfectly.
• Tailored Quality: It's easier to control the quality of SCPs. For example, scientists can make microorganisms produce more of a certain protein or vitamin.

Things to Consider

Even though SCPs are great for human food, there are some things that make it harder for them to be used everywhere:

• Nucleic Acid Levels: Fast-growing microbes like bacteria and yeast have a lot of nucleic acids (like RNA). If people eat too much of this, it can lead to health problems like gout or kidney stones. For human food, these nucleic acids need to be removed. One way to do this is by heating the cells.
• Hard-to-Digest Parts: Some microorganisms, like certain algae and yeast, have cell walls that are hard to digest. These cells might need to be broken open so our bodies can get to the good stuff inside.
• Taste and Color: Some SCPs might have an unpleasant color or taste.
• Contamination: It's important to make sure other unwanted microbes don't grow with the SCPs. These unwanted microbes could produce harmful substances. One smart way to avoid this is to grow a fungus called Scytalidium acidophilum. It grows in very acidic conditions (pH 1), where most other microbes can't survive. This allows it to grow on cheap, acid-treated paper waste.
• Missing Nutrients: Some yeast and fungal proteins don't have enough of an important nutrient called methionine.